The HDTV (digital high definition widescreen television) system proposed for use in the United States is totally incompatible with the NTSC broadcast standard in use today. Some primary differences between the two systems are: the HDTV system is digital while the NTSC system is analog, the HDTV system uses a 16:9 aspect ratio while the NTSC system has a 4:3 aspect ratio, the HDTV system will have 1125 television scan lines while the NTSC system has only 525. Thus, if the broadcasting industry immediately adopted the digital HDTV system and abandoned the NTSC system, perfectly serviceable NTSC television receivers purchased within the last few years would be rendered obsolete and useless. To avoid such a result, it is currently envisioned that the transition from conventional analog NTSC-standard broadcasts to digital HDTV television broadcasts will occur over a period which may last some fifteen years to allow for normal attrition of the older NTSC television receivers. During this period, television stations may "simulcast" (i.e., simultaneously broadcast) their programs on two television channels allotted for their use by the FCC (Federal Communications Commission). Each of the two channels will encompass 6 MHz of bandwidth, and need not be contiguous. One of the two channels will be the currently assigned analog NTSC channel, and the other will be assigned for transmission of HDTV material.
It is not expected that all television stations will begin broadcasting HDTV signals on the same day. Instead, the television stations in a given geographic area will most probably begin HDTV transmissions over a period of a few weeks, months, or even years, as their individual finances permit. It is envisioned that television receivers produced during the transition period will include both an HDTV tuner and signal processing section, and an NTSC tuner and signal processing section. In this way, the television receiver could receive and display signals of both systems.
As noted above, each television station in a given geographic area will have two channels assigned to it. It is most likely that these channels will not be contiguous, nor even have a nationwide pattern of channel pairing due to the realities of spectrum crowding. That is, there will be no fixed relationship the NTSC channel number and the HDTV channel number.
Nevertheless, despite that fact that the signals are carried on two distinct frequencies, and are actually incompatible, it is likely that the viewer will come to regard the transmissions as one television channel, because the same television program may be carried simultaneously on both channels. That is, a version of a given television program in the NTSC format may be aired on the NTSC channel at the same time that its corresponding version in the HDTV format is aired on the paired HDTV channel of the same television station. The nontechnical viewer, not fully understanding the system distinctions, will naturally expect to tune his desired television program with a single selection, just as he has done in the past.
In order to free the viewer from having to remember that NTSC channel 4 (for example) is paired with HDTV channel 41 (for example), a tuning-setup procedure will be provided so that the viewer may specify which channels are paired in his given geographic area.
A dual-system (i.e., High Definition TV/NTSC) television receiver is known from the Sony KW-3600HD television receiver, produced and marketed in Japan by Sony Corporation in 1990. The KW-3600HD includes circuitry to receive and display NTSC signals and High Definition analog signals (i.e., the MUSE system). It is noted that in Japan there are only two MUSE channels, and consequently, they are not "paired" with a corresponding NTSC channel.
It is known from U.S. Pat. No. 4,600,918 (Bellisomi et al.), and also from U.S. Pat. No. 4,959,720 (Duffield, et al.), to associate a label (e.g., WNBC) with a channel number, and thereafter, tune the desired channel by entering its label. However, as noted above, viewers will likely come to regard the HDTV and NTSC broadcasts which are transmitted from the same station as a single channel, and therefore the viewer will expect each station to have only one label (i.e., WTTV). Thus, a problem exists in how to perform a tune-by-label function in a combined HDTV-compatible and NTSC-compatible television receiver when at least some television stations have both an NTSC channel and an HDTV channel assigned to them.